java - 在多对多关系的情况下获取结果

Question

我有三个表

1. employee:存储员工信息

2. role_description:存储我拥有的角色类型，例如管理员、区域经理、国家/地区经理

3. employee_role_details:员工和角色描述与一些额外字段之间存在多对多关系。

现在，我在从员工表中获取包含 (employee_id, email)，从 employee_role_details 中获取包含 (role_ownership, role_id) 以及从与 role_description 中的 role_id 对应的 role_description 中获取(role_name 和 role_description)的结果时遇到问题。

员工.java

@Entity
@Table(name = "employee", uniqueConstraints= @UniqueConstraint(columnNames={"employee_email"}))
public class Employee {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "employee_id")
    private long employeeId;

    @Column(name = "employee_name")
    private String employeeName;

    @Column(name = "employee_email", unique = true, nullable = false)
    private String employeeEmail;

    @Column(name = "contact_no")
    private String contactNo;

    @Column(name = "password")
    private String password;

    @Column(name = "is_active")
    private Boolean isActive = true;

    @Transient
    private long EmployeeRoleId;

    @Transient
    private String roleName;

    @Transient
    private int totalpage;

    @OneToMany(mappedBy = "employee", cascade = CascadeType.ALL)
    //@JsonIgnore
    @JsonManagedReference(value = "employeeRoleRecord-employee")
    @LazyCollection(LazyCollectionOption.FALSE)
    private List<EmployeeRoleRecord> roleRecords = new ArrayList<>();

    @OneToMany(mappedBy = "assignedTo", cascade = CascadeType.ALL)
    @JsonManagedReference(value = "complaint-treatment-employee")
    @LazyCollection(LazyCollectionOption.FALSE)
    private List<ComplaintsCategory> complaintCategoryAssignedTo = new ArrayList<>();

员工描述.java

@Entity
@Table(name = "role_description")
public class RoleDescription {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "role_id")
    private long roleId;

    @Column(name = "role_name")
    private String roleName;

    @Column(name = "role_description")
    private String roleDescription;

    @Column(name = "status")
    private boolean status;

    @OneToMany(mappedBy = "description", cascade = CascadeType.ALL)
    @JsonManagedReference(value = "employeeRoleRecord-roleDescription")
    @LazyCollection(LazyCollectionOption.FALSE)
    private List<EmployeeRoleRecord> roleRecords = new ArrayList<EmployeeRoleRecord>();

员工角色记录

@Entity
@Table(name = "employee_role_record")
public class EmployeeRoleRecord {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "employee_role_id")
    private long employeeRoleId;

    @Column(name = "role_ownership")
    private String roleOwnership;

    @Column(name = "status")
    private boolean status = true;


    @ManyToOne(cascade=CascadeType.ALL)
    @JsonBackReference(value = "employeeRoleRecord-employee")
    @JoinColumn(name = "employee_id")
    private Employee employee;

    @ManyToOne(cascade=CascadeType.ALL)
    @JsonBackReference(value = "employeeRoleRecord-roleDescription")
    @JoinColumn(name = "role_id")
    private RoleDescription description;

    @Transient
    private long roleId;

dao 中的代码

public Employee getEmployeeByEmail(String email) {
        return (Employee) sessionFactory.getCurrentSession()
                .createCriteria(Employee.class)
                .add(Restrictions.eq("employeeEmail", email)).uniqueResult();
    }

服务:

public Employee getSurveyData(String employeeEmail){

        Employee loggedInEmployee =
                 loginDao.getEmployeeByEmail(employeeEmail);

        Employee  loggedInEmployeeRecord = new Employee();

            loggedInEmployeeRecord.setEmployeeId(loggedInEmployee.getEmployeeId());
            loggedInEmployeeRecord.setEmployeeName(loggedInEmployee.getEmployeeName());

            List<EmployeeRoleRecord> employeeRoleRecords = loggedInEmployee.getRoleRecords();

            List<EmployeeRoleRecord> employeeRoleRecord = new  ArrayList<>();

            for(EmployeeRoleRecord record :  employeeRoleRecords){

                EmployeeRoleRecord employeeRole = new EmployeeRoleRecord();

                employeeRole.setRoleId(record.getDescription().getRoleId());
                employeeRole.setRoleName(record.getDescription().getRoleName());
                employeeRole.setRoleOwnership(record.getRoleOwnership());
                employeeRole.setStatus(record.isStatus());
                employeeRoleRecord.add(employeeRole);
            }

            loggedInEmployeeRecord.setRoleRecords(employeeRoleRecord);


         return loggedInEmployee;
    }

输出:

    {
  "employeeId": 1,
  "employeeName": "Dhyanandra Singh",
  "employeeEmail": "admin",
  "contactNo": "9893651872",
  "password": "123456",
  "isActive": true,
  "roleRecords": [
    {
      "employeeRoleId": 1,
      "roleOwnership": "overall project",
      "status": true,
      "roleId": 0,
      "roleName": null
    }
  ],
}

问题:

我得到的 json 输出在角色记录列表中不包含角色 ID 和角色名称。

Answer 1

问题是:

您在 EmployeeRoleRecord 类上的 roleId 属性映射为@Transient，这意味着它不会持久保存在数据库中，因此 Hibernate 无法获取该字段的结果。

查看您的类建模，我无法弄清楚您试图用 roleId 映射什么，我建议两种可能的方法:

1. 不要直接返回您对 getEmployeeByEmail 方法的查询。首先获取结果，然后迭代它并在每条记录上手动设置您想要的所需 roleId；

2. 检查您的模型方案并为 roleId 进行正确的映射，它可能应该引用另一个实体，因此请确保正确映射关系以便在单个查询中获得结果。

祝你好运。